Combined torsiograph and torsiograph calibration device



April 14, 1953 L. F. HOPE 2,634,604

COMBINED TORSIOGRAPH AND TORSIOGRAPH CALIBRATION DEVICE Filed DSC. 6, 1947 Bnventor Patented Apr. 14, 1953 COMBINED TORSIOGRAPH AND TORSIO- GRAPH CALIBRATION DEVICE Lawrence F. Hope, Grosse Pointe Farms, Mich., assgnor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 6, 1947, Serial No. 790,202

(CI. 'I3-1) 7 Claims.

'I'his invention relates to calibrating means and more particularly to self-generated Calibrating signal means simultaneously vapplied to indicating means along with the measuring or testing indications, to provide the operator with an accurate gauge by which to weigh the values of the resultant indices being tested or measured.

There are many instances in which fixed or predetermined calibrations cannot be directly applied to resultant curves obtained by test, but which at best give only approximate values. This is due in the main to the fact that the particular theoretical operation is not too closely followed by the actual results obtained, and therefore the theoretical calibrations do not too closely apply. If some means could be actuated by the apparatus during its own operation to generate calibration signals and these signals applied as indices of position, amplitude, etc., then this would be a simultaneous generation of the test results, and at the same time a superimposed calibration chart, which would be highly accurate inasmuch as it Would follow any variation in the actual tests. An illustration only,of one eld in which my invention could be highly useful, is the calibration of torsiograph means, which has in the past been quite diliicult to check or accurately calibrate. Equipment of this general order is described in one of my earlier patents' #2,399,635, issued May 7, 1946, in which case torsional vibration is measured by the device and a resultant curve showing the same appears on the head of a cathode ray oscillograph, the amplitude of the curves there appearing indicating the amount of torsional vibration. A sample curve is shown in Figure 12 of that patent. This unit has ample precision for normal test work, but in cases Where extreme accuracy is required, as for instance when the instrument is used to determine the accuracy of other torsiographs, further assurance of accuracy is desirable.

It is, therefore, an object of the present invention to provide means for simultaneously generating calibration indications Iand normal test indications so that the two are subject to the same practical variations.

It is a further object of my invention to provide apparatus capable of producing calibration indications simultaneously With actual test curves obtained from test equipment. y

It is a still further object of my invention to provide calibration indications which can serve as standards against which other test runs being made on equivalent apparatus simultaneously can bev checked.y 1- f will become apparent as the specification pro- Y ceeds, my invention will be best understood by reference to the following specification and claims and the illustrations in the accompanying drawings, in which:

Figure 1 is a schematic block diagram showing a form of my invention.

Figure 2 is a graph of a wave form generated in a portion of the system of my calibration means. Y

Figure 3 is a graph showing the standard pattern obtained in a test run of a torsiograph.

Figure 4 is a graph of a sawtooth wave form widely separated, generated in another portion of the system of my calibration circuit; and

Figure 5 is a final resultant record showing the Wave form obtained by test and calibration marks.

vFigure l illustrates one application of the calibrating system which is the subject of this patent application. In this case, a torsiograph of any type (indicated by the dotted outline 2) is tested by subjecting it to a torsional oscillation excited by -a mechanism indicated at I0, such, for example, as that illustrated in Figure 4 of Van Degrift #2,522,472, dated September 12, 1950. 'This is rotated, through exible coupling 8, by motor 6. There are, of course, several Ways in Which variations in torsional speed are induced for test purposes.

The phase shift torsiograph previously referred to has, because of its inherent design, what might be called built-in calibration. In other Words, the value of the height of each saw-toothed wave in degrees is determined by the spacing of the teeth in degrees. If, for example, teeth are provided in the generating gear, each saw-toothed wave has a calibrated value of three degrees. Other factors, however, enter in, which may vary the theoretical calibrated figure due to, for example, imperfect shape of saw-toothed waves which might cause a correction factor to be introduced. Therefore, while no large error may be introduced, still for high accuracy it is desired to provide additional scale checking means.

To indicate the amplitude of vibration `being applied, a phase shift torsiograph such asthat shown in Patent #2,399,635 is operated simultaneously with the instrument being tested. VIn

3 order to improve assurance of accuracy of the phase shift torsiograph thus being used, its usual arrangement is altered in a manner which illustrates the subject calibration method.

A gear I4 is driven by a motor Si through shaft l2 and iiexible coupling 3, and is therefore subject to any variations in torsional speed which are applied thereto and'which appear in the shaft 4. On the driving side of motor 6 there is not intended to be any variation in amplitude, and the motor directly drives two gear wheels I6 and i8. The teeth of these various gear Iwheels I4, IB and I8 are adapted to generate pulses by changing `the magnetic elds'of-pick-up coils 20, 22 and 24 respectively as theyrotate past the same. Pick-up coil 20 is connected to a pulse shaper 25, the pulse being fed through line 28.

to mixer 3U. Pick-up coil 22 is connected in like manner to a similar pulse shaper 32, and thence through conductor 34 to the mixer' 3i). Pick-up coil l'2411s connectedfto a third pulse shaper 38, the output-of which is fed to a synchronized sawtooth oscillator 38, the output of the latter being connected through line t@ to the Y axis terminal ofan oscilloscope. The mixer 3U has its output connected through line 42 to the Z axis or brightness'control terminal of the same oscilloscope for controlling the beam intensity.

The'number of teeth on the two gears i4 and I8'isidentical-and'in one of the systems satisfactorily operated by me, 120 teeth were used and were satisfactory. This again, of course, is merely exemplary. On the other hand, gear i carries a proportionately different number of teeth in order to generate a series of progressive pulses incombination with one of the other gears, and as an example, 144 teeth were utilized for this gear in one of the systems. The gear wheel I8 with its'associated pick-up coil 24, pulse shaper 36; and synchronized saw-tooth oscillator, corre- E 1 spends-to a `portion of the torsiograph .set forth in Patent #2,399,635, in that it provides a synchronized saw-tooth wave such as 22 in Figure 2. The only diferenceis that the pulse generated bylthe pickup 24 is now not used. This results inonly a saw-toothed wave of the proper frequency being fed to the vertical deflector means ofthe oscilloscope. superimposed upon this sawtooth wave and at some intermediate position between the two ends as the trace appears on the oscilloscope, is a pulse generated by the gear I4 and-transmitted by its pick-up coil 20 through the pulse Shaper 26 and the mixer 38 to the Z axis terminal of the oscilloscope. This causes a spot tobe formed on the saw-tooth wave whose vertical position depends upon the amount of torsional vibration present which, of course, is continuously changing and provides a wave form similar to that-shown in Figure 3, where all 'of the saw-tooth waves are compressed more closely together and the superimposed pulses or bright spots (since this pulse controls the intensity of the beam) form the indicating wave.

So far this operation corresponds to a torsiograph of the type previously described in my patent above identied, and any variation in the phase relation between shaft l2 and shaft 4 will show up to form a wave on the head of the cathode ray tube as distinguished from a straight line if no vibration is present. The flexible coupling permits a certain variation in shaft speed between the two and mechanism it induces such changes. By having shaft 4 connected to a torsiograph as before identified, if-the two torsiographs areoperating correctly, thereadings on one should be identical with those on the other. Up to this point the pattern appearing on the screen is identical in principle to that of the previously mentioned patent. Therefore, the approximate inherent calibration also applies to this pattern. For further accuracy it is desired to incorporate some means for indicating directly to the operator exactly howv much in angular degrees this deflection is. The pulses provided by the gear I6 are for this purpose and applied to the mixer through the pulse Shaper 32 are likewise impressed upon the Z axisterminal oi the oscilloscope, and control the beam intensity. As in the case of the pulses applied through the piek-up coil 2B, they form bright spots on the zigzag saw-tooth -wave at a regular series of positions controlled by the proportionality between the number of teeth in this gear and the others. This is more clearly shown on Figure 4, where the saw-tooth wave 4B alone is shown, having thereon a series of bright spots 48, whose position changes with geometric regularity, depending upon the ratio. Ii this series of sawtooth waves is now compressed together, there will appear a series of horizontal dotted lines such as that shown on Figure 5 at 56, which are superimposed upon the wave 52, which is a traceof the torsional vibration. The saw-tooth wave does not show in Figure 5 as its luminosity is so much less than the others that itfades into the background. The Vertical spacing between each one of these horizontal dotted linesis representative of a certain number of arcuate degrees in the shaft, and, therefore, by having the two patterns superimposed, the operator can read directly the number of arcuate. degrees vibration that the unbalance forces in the shaft cause. Generalizing, the saw-tooth wave is provided and synchronized by the pulse generated by gear I8, and upon that saw-tooth wave there are impressed pulses by gear i4 which vary from a horizontal line, depending upon torsional vibration. This provides the irregular curve through the center ofrFigure 5 to dene the torsional vibration. Simultaneously, gear I6 generates ata proportional rate, pulses which provide the series of horizontal dotted lines 50, indicating different arcuate distances, and thus enables the operator to directly and immediately ascertain how far the unbalance forces are causing the shaft to twist. Having thus obtained a much more accurate measurement of calibrator amplitude, one is in a position to determine the accuracy of any torsiograph which may be attached to shaft 4.

It is obvious that my method of superimposing a proportionate set of pulses to provide calibration lines could be used in a number of different installations, and that this disclosure, as applied to torsiograph means and using a cathode-ray oscilloscope, is merely illustrative.

I claim:

1. In Calibrating and testing means for measuring torsional vibration in a rotating body, driving means, resilient means connecting the driving means tothel body, pulse generating means driven by and subject to the vibration of the body, two pulse generating means directly driven by the driving. means and insensitive to the vibration, said last named pulse means having diierent rates o pulse generation, pulse shaping means connected to each of the pulse generators, and a cathoderay Oscilloscope having a plurality of control circuits, conductive means connecting the pulse shaping means connected to the pulse generating'means subject to vibration of the body to one of the control circuits, andv conductive means connecting one of the pulse shaping means connected to one of the pulse generating means driven by the driving means to said one of the control circuits of the oscilloscope, and further conductive means connecting the remaining pulse shaping means to another control circuit of the oscilloscope so that a series of superimposed signals will be applied to the screen.

2. In calibrating means for measuring the torsional vibration of a rotating body, driving means for rotating said body, an oscilloscope having vertical deiiection means and intensity control means, oscillator means for generating a desired Wave form connected to the vertical deflection means, a rst pulse generator driven by said driving means and connected to the oscillator to control the same, a second pulse generator driven by the driving means, a third pulse generator driven by the body being tested and subject to the vibration thereof, and conductive means connecting the second and third pulse generating means to the intensity control means so that they will superimpose a double pattern on said wave form.

3. In calibrating means for measuring the torsional vibration of a rotating body, driving means for rotating said body, an oscilloscope having vertical deflection means and intensity control means, oscillator means for generating a desired Wave form connected to the vertical deflection means, a iirst pulse generator driven by said driving means and connected to the oscillator to control the same, a second pulse generator driven by the driving means, a third pulse generator driven by the body being measured and subject to the vibration thereof, pulse shaping means connected to both the second and third pulse generating 'means and conductive means connecting each pulse shaping means to the intensity control of the oscilloscope to develop patterns thereon.

4. In Calibrating means for measuring the torsional vibration of a rotating body, driving means, resilient connecting means between the driving means and the body to insulate the driving means from the torsional vibrations of the body, an oscilloscope having vertical deflection and intensity controls, wave generating means connected to the vertical deflection control of the oscilloscope, a pulse generator connected to the driving means and to the wave generator to control the same, a second pulse generator of the same frequency connected to the body and subject to the vibrations'thereof, a third pulse generator having a set frequency diierence to the rst pulse generator connected to the driving means, connecting means for joining the second and third pulse generators to the intensity control for the oscilloscope.

5. In calibrating means for measuring torsional vibration of a rotating body driven by a driving means through a resilient connection, an oscilloscope having vertical deflection and intensity controls, wave generating means connected to the vertical deflector means, a plurality of pulse generators driven directly by the driving means and having different predetermined frequencies, connecting means between the wave generator and one of the pulse generators and between the intensity control means and another of said generators, a further pulse generator connected to the rotating body and subject to the vibrations thereof also connected to the intensity control means so that the wave generator synchronized with the drive provides a background pattern and the two pulse generators connected to the intensity control provide superimposed patterns thereon.

6. In calibrating means for indicating the torsional vibration of a rotating part, driving means for the part, resilient means between the driving means and the part to insulate the driving means from vibrations of the part, indicating means, a plurality of pulse generating means, one actuated by said part and subject to the vibration thereof, and the other actuated by the driving means, conductive means for connecting both pulse generators to the indicating means to provide indications of torsional vibration, and a further pulse generator actuated by the driving means and unaffected by vibration-s of the part, having a dif-'- ferent rate of pulse generation from the other pulse generator actuated by the driving means, and independently connected to the indicating means to provide calibration indicia.

'7. In calibrating means for measuring the torsional vibration of a rotating body, driving means, resilient connecting means between the driving means and the body to insulate the driving means from the torsional vibrations of the body, -an oscilloscope having vertical deflection and intensity controls, wave generating means connected to the vertical deflection control of the oscilloscope, a pulse generator connected to the driving means and to the wave generator to control the same, a second pulse generator of the same frequency connected to the body and subject to the vibrations thereof, a third pulse generator having a set frequency dil-ference to the rst pulse generator connected to the driving means, pulse shaping means connected to both the second and third pulse generating means, a mixing circuit oonnected to the output of both last-named pulse shaping means, and conductive means connecting the mixing means to the intensity control of the oscilloscope.

LAWRENCE F. HOPE.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,208,648 Schrader July 23, 1940 2,399,635 Hope May 7, 1946 

